4GB Of Memory in 32-Bit XP

[Kobalt]

As far as I remember, XP 32-bit SP2 only can recognize around 3.2GB of RAM. However, I'm having trouble finding a reputable source on this. Where I work, we provide computer support, and one of our "customers" is complaining that his system with 4GB of RAM is only showing up with 3.2GB. I told him that this is a 32bit XP limitation, but he won't believe me, hence the need for a good source on this topic.

While searching for a good source I saw a lot of sites that say 32bit windows can see 4GB of memory and some that say it can only support a little over 3GB. I'm a bit confused on this...

[Ominous Gamer]

http://windowssdk.msdn.microsoft.com.../ms694080.aspx

[bachus_anonym]

http://support.microsoft.com/kb/888137/en-us

[Kobalt]

http://windowssdk.msdn.microsoft.com.../ms694080.aspx

That says it supports 4GB, which clearly isn't the case if I haven't seen a 32bit system recognize 4GB.

http://support.microsoft.com/kb/888137/en-us

So should I add the /pae command? That article was kind of confusing...

[bachus_anonym]

So should I add the /pae command? That article was kind of confusing...

Actually, PAE is already enabled on Windows XP SP2 as it's neccessary for hardware-enforced DEP on A64 processors and you can see it on e.g. my example screenshot - PAE enabled and 3.5GB recognized in System Properties. Windows XP Professional 64-bit, for instance, is what you'd need to have 4GB fully addressed - older another example here.

[comrad]

32bit Windows only recognizes 3.2gb of ram

[comrad]

Link him to that post^^^^ :P

[Kobalt]

Hmmm...maybe I will put x64 on there. I just checked a software compatibility list and pretty much every program we use works (except realplayer, but ill just put the alternate on it). It wasn't clear on Matlab 7.0 though. I'll just tell him since 64-bit is twice the number as 32-bit, then its twice as fast lol.

I wish i could link him to it. I need an article or kb that simply states winxp sp2 only supports 3.Xgb!!!!(@*%&!@%!!!%(*!&

This guy is a major pain in the ass...he's a mathmatician and he thinks hes better than everyone. He's also having some problem with adobe acrobat and hes telling us what he wants us to do with his computer. Do it yourself mr. smarty pants . He also wanted us to RMA the fourth 1GB DIMM because he was 100% sure it was bad since only 200mb of it was being recognized. Thank god he's not in charge .

edit: why do some systems only show 3.2GB and others like bachus' show 3.5gb.

[uOpt]

PAE in 32 bits should enable the full 4 GB, not 3.3-3.7 as you see in XP SP2.

Supposedly before SP2 XP could do that, too, but by now it seems to be limited to the Unixes and possibly Win2K 32 bit.

I have never seen an explanation why MS pulled full working PAE in SP2.

[couppi]

Windows 32bit can address around 4gb of ram, but devices tend to allocate a piece of that to themselves. The graphics card might take 512mb, then the NIC card could take 16mb, the sound card will take some up, and pretty soon you're left with only 3.2gb ram.

[Ominous Gamer]

Windows 32bit can address around 4gb of ram, but devices tend to allocate a piece of that to themselves. The graphics card might take 512mb, then the NIC card could take 16mb, the sound card will take some up, and pretty soon you're left with only 3.2gb ram.

That doesn't make any sense, because users with only 512mb of ram would be in the negative before even booting the desktop.

[uOpt]

Windows 32bit can address around 4gb of ram, but devices tend to allocate a piece of that to themselves. The graphics card might take 512mb, then the NIC card could take 16mb, the sound card will take some up, and pretty soon you're left with only 3.2gb ram.

No, you mix that up.

Device space is below 4 GB, usually 3.3-4.0 GB but it can be less or more. You cannot have RAM live in the same space, so the BIOS blends out the RAM at those locations if you have 4 GB of RAM, leaving you with 3.3 GB visible.

To get the RAM that the BIOS blends out back you can re-map it to above 4 GB where there is no conflict with device space. That's also done by the BIOS (often not correctly).

But then the OS needs to see RAM that lives above 4 GB. Even if you only have 4 GB of RAM, it now lives on 0.0-3.3 GB and 4.0-4.7 GB (or similar), so even those you don't have more than 4 GB some of your RAM lives at above the 4 GB boundary. To use the RAM from 4.0-4.7 GB you either need a 64 bit OS.

Or an OS with working PAE. Windows 32 bit used to have working PAE but it has been removed in XP SP2. Other 32-bit OSes with PAE can happily use the RAM from 4.0-4.7 GB, such as FreeBSD, Linux and other versions of Windows, including (so I have been told) XP before SP2.

[Kobalt]

"We have found that applying Service Pack 2 (SP2) to Windows XP
imposes a ~3gb limit for memory. All 4gb will be there, but XP SP2
only "sees" ~3gb. This is called a "security fix" to ward off memory
exploits in Windows.

Running with no service pack or SP1 will allow all 4gb to be reconized
by Windows XP." -AndyT OCZ Memory

I referred him to that...we'll see if he believes me now.